Cleft lip and palate (CL/P) is a major congenital structural anomaly that is notable for significant lifelong morbidity and complex etiology.. The extensive psychological, surgical, speech and dental involvement emphasize the importance of understanding the underlying causes. For the investigator, cleft lip and palate, like other complex diseases, provides a challenge in determining the multiple genetic, environmental and stochastic factors that lead to its phenotype. In this proposal, we will pursue the complex causes of cleft lip and palate through our investigations of a genetically simple form of clefting, Van der Woude syndrome (VDWS). VDWS is the most frequent syndromic form of cleft lip and palate and the form we fell is best suited to contribute to an increased understanding of the more common non-syndromic form of cleft lip and palate and the form we feel is best suited to contribute to an increased understanding of the more common non-syndromic form. Specific goals in this project will include: 1) identification of the VDWS gene. A genetic screen for disease-causing micro-deletions will be used to further restrict the region that contains the VDWS gene. Powerful gene-finding techniques, including the sequence analysis of the entire critical region, will be used to identify transcriptional units. Mutation screens will then be used to find disease causing changes in the DNA. Extensive mutation screens will be performed to search for functional domains. 2) characterization of the VDWS gene and its mouse homolog, including complete cDNA and genomic sequence analysis, the study of temporal and tissue-specific expression to identify developmental pathways that require the VDWS gene functional and screens for gene homologs which may function in the same pathway. 3) identification of sequences that regulate VDWS gene expression and the development of transgenic mouse models, including a mouse knockout that will be used in 4) long-term studies that will include complementation experiments to identify other genes in the pathway and investigate the effects of environmental factors on the VDWS gene and other genes in the same pathway. The impact of this project is that studies of CL/P are valuable, both for the importance of the defect itself as a contributor to morbidity and for providing a model for a complex human birth defect. The identification of the VDWS and VDWS-like genes will immediately provide for better risk counseling, and their characterization under environmental stresses hold the promise for contribution to preventative strategies and improved therapeutics. In addition, the identification of the VDWS gene is relevant to studies of CL/P because of its similarities to the more frequent non-syndromic forms of CL/P and because it will provide a foothold into the earliest steps of craniofacial development.